The present invention relates to a method for modifying a civil engineering structure through reinforced soil techniques, such as for a structure with reinforced fill.
The structures concerned by the invention can be of various uses such as traffic lanes, extend a constructible space, prevent damage, erosion, or fall of wall stones or rock walls, or create an esthetic material.
A reinforced soil structure generally combines a compacted fill, a facing, and reinforcements or stabilization elements connected to the facing. The stabilization elements are placed in the soil with a density dependent on the stresses that might be exerted on the structure, the thrust forces of the soil being reacted by the soil-reinforcements friction.
The facing is most often made up of prefabricated concrete elements, in the form of slabs or blocks, juxtaposed to cover the front face of the structure. There may be horizontal steps on this front face between different levels of the facing, when the structure has one or more terraces.
The stabilization elements placed in the fill are usually secured to the facing by mechanical connecting members that may take diverse forms. Once the structure is complete, the stabilization elements distributed through the fill transmit high loads, in some cases of up to several tons. Their connection to the facing needs to be robust in order to maintain the cohesion of the whole.
Although these reinforced soil structures are very robust and capable of good performance, it can sometimes be realized that it is necessary to carry out changes to the structure.
For example, a structure initially designed to support four traffic lanes may need to be modified in order to permit the placement of six traffic lanes.
It may also be the case that over time the facing is degraded due, for example, to an initially unintended use of the structure or because of a construction defect of the facing.
The concrete facing elements can undergo concrete pathologies. Among the concrete pathologies known by the person skilled in the art which can lead to swelling of the facing elements, examples include alkaline reactions occurring within the concrete or internal sulphate reactions.
The internal swelling of crystals can lead to cracking followed by progressive breakdown of the concrete composing the facing. This swelling can take place over several months or several years. However, it is not detectable at the time of the production of the structure and this swelling may also be accelerated by unfavorable weather conditions.
The facing elements of a reinforced soil structure play an important role in the stabilization of the structure. Moreover, these facing elements also play an important architectonic role.
In the case of irremediable pathologies or facing element degradation, it may sometimes be necessary to restore the mechanical role of the facing by carrying out a repair.
Currently, the repair solutions essentially consist in replacing damaged or degraded facing elements.
The methods that are currently known by the person skilled in the art generally comprise the steps of:                stabilizing the fill by injection of concrete behind the facing element,        cutting the facing element,        removing it fragment by fragment, and        casting a new facing element in place or replacing the old facing element by a prefabricated element.        
The replacement of facing elements one by one is a long, meticulous process, presenting risks. In particular, it is necessary for large size structures to arrange a preliminary stabilization, for instance by injection of grout or resin in the fill material behind the facing elements. In fact, there is a risk of rock slide or erosion during the operation of withdrawal of the facing elements.
Therefore, there is a need for a method permitting to repair and/or modify a reinforced soil structure that does not have the shortcomings of the methods according to the prior art.